BODY RESISTANCE 



A consideration of this table leads us to adopt the following 

 working rule for Case (2): Work out the actual full scale re- 

 sistance at 100 miles per hour, and for other speeds, take the 

 V 2 law, working from the value so obtained. This certainly 

 introduces errors, but these are quite small for high speeds, 

 while for low speeds, as will be evident at a later stage, resist- 

 ance errors do not affect the performance of a machine at all 

 seriously. 



Passing now to the consideration of Case (3) and taking a 

 stream-lined strut as an example, say a strut 2-J- inches wide 

 in the direction transverse to the wind on a machine doing 

 1 20 miles per hour, we shall have to work from a wind tunnel 

 test on a strut of similar shape but only I inch wide and tested 

 at a speed of 27 miles per hour. 



Then if we make the quite reasonable assumption that in 

 this case 



resistance = X(/V) 1>0 



where X is a constant, we get 



resistance = 



X/ 2 V : 



and we can obtain the following table :- 



